JavaScript Set() with specific key to hash on [duplicate]

Question

I have a few objects that are all disparate, but which all have an id field. I want to create a Set() to hold these, but am not sure how to specify this field to the Set constructor/prototype/etc. Is this doable?

Let's say I have two types of objects (I'll give typescript definitions for simplicity's sake):

interface Thing1 { id: string; someData: string[] } interface Thing2 { id: string; someString: string; someOtherString: string }

Now, I have two Arrays of these things, let's call them

array1: Thing1[]; array2: Thing2[];

What I'd like to do is create a new Set(array1) and then add each Thing2 in array2, performing a conditional merge of the two arrays.

The unique key in each of these is the id field - I was hoping there was some overloaded constructor or similar pattern that could be given a lambda (a la new Set(array1, (item) => item.id), maybe) which would specify the key to hash on for identity.

Your question isn't very clear. Explain yourself better, and add code to show what you're trying to achieve — Nitzan Tomer
– Nitzan Tomer, Commented Apr 14, 2017 at 0:26
Is this what you are asking? stackoverflow.com/questions/29759480/… — user886
– user886, Commented Apr 14, 2017 at 0:30

Badacadabra · Accepted Answer · 2017-04-14 00:39:39Z

Working with a Set is pretty straightforward...

Imagine that you have two objects like so:

const obj1 = { id: 1, prop: 'Foo' }; const obj2 = { id: 2, prop: 'Bar' };

To create your Set with references to these objects, you can do this:

let set = new Set([obj1, obj2]);

Or that:

let set = new Set(); set.add(obj1).add(obj2);

Since a Set is an iterable object, you can use a for...of loop to retrieve all your data:

for (const obj of set) { console.log(`${obj.id}:${obj.prop}`); }

Not quite what I meant - I've added some examples, but it looks like the answer is just "You can't do that in JS"
Oh, I see... I am sorry, your description was a bit unclear. I thought you wanted to know how to use the data structure in a traditional way. ;)

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